Of all the places red bus drivers get to hang around, SouthEndGreen's one of the nicest. A proper caff by the bus stop, for a cup of coffee or a croissant. A genuine tearoom across the road, a bookshop and a bespoke bakery. A newsagents for topping up with fags, plus an M&S Simply Food. An old school set of underground conveniences, so much nicer than having to relieve yourself in a smelly portaloo at the end of your shift. And best of all a Victorian Tramwayman'sShelter, its timber frame recently restored, within which the busmen can hide away. This is the less bohemian end of Hampstead, ideally situated for the Heath and the Royal Free, but not quite so eye-wateringly exclusive as the villas further up the hill. For the 24 it's downhill all the way, from the headwaters of the Fleet to the mouth of the Tyburn. Departing about every 4-8 minutes.

At the firststop I head, as usual, to the front of the top deck. I'm joined by a vision in mustard, or at least an elderly bloke with trousers of this unforgiving hue. He's wearing a tweed jacket on top, a shirt I can only think was once a tablecloth, and unforgiving bright white socks below. I'm trying not to look at his hair, undoubtedly Brylcreemed, which is impressive attention to detail for a toupee. He launches into the Guardian quick crossword, replaced eventually by a Susan Sontag paperback, so very Hampstead. We'll be sharing upstairs for a while, we two, as most passengers prefer the cramped convenience of the lower deck.

The driver careers past Victorian terraces towards more concretey Camden estates, setting off an electronic "Slow Down" as he passes. The landscape's a typical mix of old and new, with a left hand view familiar to the omnibus rider of 100 years ago and a right hand view most definitely not. Leverton & Sons have been funeral directors round these parts since 1789, and "Bubbles" a laundrette for rather shorter. An Irish voice beats on the rear doors at Queen's Crescent, "would you open the door please and let me out?" The driver obliges, and our tour of mixed architecture continues.

For one brief minute the southbound 24 is permitted access to the joi de vivre of Camden via the Chalk Farm Road. Past the Barfly's music room, past the bling and noodle shops of The Stables Market, past a lady giving out veganism leaflets while dressed as a pink squirrel. I'm making this journey midweek so it could be busier, but the area's lively enough with Euro-youth for whom this is Central London, not some stuffy palace and square down south. But the one-way system kicks in, and we're diverted down some lesser parallel streets, our hip interlude cruelly squashed. The canal passes, and the local Sainsbury's that looks like the aliens landed, but it's a poor swap for cool.

We re-emerge on the 100-year-old route by the Camden Palace, now Koko, before rounding the glories of Mornington Crescent tube (where the ground floor is now occupied by a cab company). The run down to the Euston Road combines Georgian pillared villas, an Art Decocigarette factory and three lofty tinted tower blocks. The man behind me suddenly points towards a well-known London landmark and asks, falteringly, "what is that?" When I reply "the BT Tower" he's none the wiser, with that particular company having no brand presence in his country, which it turns out is Chile. "Financial?" is his next question, to which I decide I have no comprehensible verbal response so wave my phone in the air and that seems to satisfy.

Sorry, I've not previously mentioned I made this journey during the Olympics, and my unwitting tourist companion is in fact some member of the Chilean coaching squad, resplendent in official white and blue tracksuit. I'm not sure why he's heading from Camden to Pimlico, I'm not certain he is either, but I try to answer his three syllable requests as best I can as the journey continues. We'll be spending a lot of time in each other's company down Gower Street, close to the Olympic press hub in Russell Square, where rephased traffic lights trap us in a hotel canyon for at least ten minutes. "About 250 years old" I tell him, regarding the age of the local housing stock, which is about all there is to say.

Time for the switchback through the heart of town. Initially it's not the best view of the West End, past lumpen musicals and citrus office blocks, but things pick up down Charing Cross Road where a matinee crowd are queueing in Cambridge Circus. Again the architecture's well over 100 years old on one side of the road, and well under on the other. Blimey, who turned the Hippodrome into a casino, and does the Angus Steak House really serve leathery calf until one o'clock in the morning? As we approach Trafalgar Square the queuing traffic's mostly buses and taxis, and look, there's the Paralympic clock still ticking down into the teens. All the bustle of Games-time London is here, and the 24 has a grandstand view.

As we career into Whitehall the driver beeps his horn and the pedestrians scatter. Normally it's busy down here but the beach volleyball's underway on the adjacent parade so the pavements are fenced off and clear. Outside Horseguards the mounted sentries are entirely unhassled by cameras, which they must be loving, but no smile drips forth beneath their bearskins. Cyclists make the most of their four-lane freedom - Whitehall genuinely is a Cycle Superhighway, if only temporarily.

We pass Big Ben and Westminster Abbey, having paid far less for the privilege than those in the open-topped tourist buses alongside. Only one scrap of the former peace camp remains in Parliament Square, beside a welcoming pile of flags knocked up for the Games. We make slow progress towards Victoria, not because the traffic's bad but because our driver has caught up with the bus in front and is over-keen to ensure the maintenance of headway. We pause in a layby near the cathedral, going nowhere, in sight of a large hole in the ground where something less beautiful is being built. It's taken an hour to get this far, and there's still the final mile to go.

Beyond Victoria the 24 finally gets roads of its own, streets unserved by any other bus. I'm not familiar with Wilton Road, probably for this very reason, and its posh Sainsbury's Market targeted square at locals who'd rather be in Waitrose. The flanks of Belgrave Road are lined with identikit pillared hotels, with names like Sidney, Carlton and Blades, out to attract a very specific kind of foreign visitor. My Chilean companion, after checking, finally alights at Pimlico station - maybe he's holed up in one of these hired bedrooms. And then the run into Pimlico proper, which probably isn't what you're expecting if you haven't been down here. Lupus Street divides the stucco glories of Belgravia from a fairly ordinary council estate, the sort of place one suspects Lady Porter shunted Westminster's less well-off to keep them out of sight. The charity shops, laundrettes and library are a sign of SW1's least well-known community, housed within the optimistically-named Churchill Gardens, a flat-stacked enclave that could be anywhere in London.

Of all the places red bus drivers get to hang around, Grosvenor Road's not bad. A leafy bus stand by the Thames, with views across the river to Nine Elms and the four chimneys of Battersea. It's a bit quiet, a bit nowhere, at the foot of the one-way loop round Pimlico. But it's got staying power, at the end of a bus route that's been heading the same way for a hundred years, the mighty twenty-four.